January 5, 2005, Gif-sur-Yvette, France--X-ray synchrotron beamlines contain exotic optics. For example, focusing of x-rays can be done with groups of dozens of metal refractive lenses (see Laser Focus World, September 1999, p. 24). Gratings are also important in x-ray and extreme-ultraviolet (EUV) beamlines; now, Horiba Jobin Yvon (Longjumeau, France and Edison, NJ) and Soleil have developed a variable-groove-depth (VGD) grating with exotic but useful properties.
Intended for EUV applications, the tunable blaze diffraction grating is holographic and ion-etched, with a continuously variable groove depth. By simply translating the grating parallel to the groove direction, the variable groove depth enables continuous blaze adjustment when the VGD is illuminated with a narrow beam. The first prototype, fabricated by Horiba Jobin Yvon, was tested successfully in December 2003 on the calibration beamline at the LURE synchrotron in Orsay, France before LURE was shut down. A single VGD can replace several conventional gratings; the VGD is now offered commercially by Horiba Jobin Yvon.
The VGD gratings are optimized for the new generation of synchrotron light sources. The low divergence of the beam, combined with the tunability of the VGD grating, provide a unique opportunity to scan "on blaze," maintaining optimum efficiency over a wide spectral range with a single grating. Most of Soleil's extreme-UV monochromators have been designed to exploit the VGD potential (for example, the TEMPO, CASSIOPEE, and PLEIADES beamlines).
Soleil is an extremely powerful synchrotron light source allowing the exploration of matter, inert or living. The Soleil research center will become operational in 2006. It is a storage ring accelerator, 354 m in circumference, in which high-energy electrons circulate at great velocity and produce radiation from IR to x-rays. Picked up at different locations on the ring, the radiation is energy-filtered and focused in the experiment area by x-ray optics in the Soleil beamlines. Each beamline is an actual laboratory equipped to prepare and analyze the samples to be studied and process the collected data.
As part of a continuing effort to improve the performance of fundamental optical elements of the beamlines, the Soleil optics group, in continuation of the activity of the former LURE optics group, has established a research program to improve the efficiency of the vacuum-UV and x-ray gratings.
Horiba Jobin Yvon collaborates with synchrotron centers to improve vacuum-UV and x-ray diffraction grating performance.